Coin-operated timer utilizing measurement of absolute capacitance for coin testing

ABSTRACT

A coin operated mechanism, particularly for coin-operated game machines in which the game-playing apparatus is freed by a coin so as to operate for a given length of time, comprising a pair of parallel plates forming an electrical capacitance, the coin being arranged to fall between the plates, and a circuit to determine if the absolute capacitance resulting when the coin is between the plates lies within specified upper and lower limits and if it does not operate the mechanism.

United States Patent Verrill Dec. 30, 1975 COIN-OPERATED TIMER UTILIZING 3,169,626 2 1965 Miyagawa et al. 194/100 R MEASUREMENT OF ABSOLUTE 3,645,370 2/l972 Rodwell et a].

3,682,286 8/1972 Prumm 194/100 A CAPACITANCE FOR COIN TESTING [76] Inventor: Richard Verrill, 23 RoperClose, Primary ExaminerwRobert B. Reeves Hlnmorton Rugby warw'ck5h're* Assistant ExaminerFranc'is .l. Bartuska England Attorney, Agent, or FirmW0od, Herron & Evans [22] Filed: Jan. 28, 1974 211 Appl. No.: 437,519 ABSTRACT A coin operated mechanism, particularly for coin- [30] Foreign Application Priority Dat operated game machines in which the game-playmg Jan 29 1973 United Kin dom 4449/73 apparatus is freed by a com so as to operate for a g given length of time, comprising a pair of parallel 52 l plates forming an electrical capac'tance the 1 E 2 being arranged to fall between the plates, and a c1rcu1t [58] i 100 A 101 to determine if the absolute capacitance resulting when the coin is between the plates lies within speci- [56] References Cited fied upper and lower limits and if it does not operate th h n's UNITED STATES PATENTS 6 me a 1 m 5,059,749 l0/l962 Zinke 194/100 R 5 Claims, 3 Drawing Figures WAVE GEN. 4

C RRENT imp /6 /a V RECT.

ilLIMlT. I0 2 l 5VEL LEVEL 1 EI. T DET AND 4 GATE l I0mS DELAY 34 24 l IOOmS A8 ms d, MONO- DELAY WA E STABLE 26 1 4 aoms /2o 605 30 15 SWITCH SWITCH SWITCH 2 l I CHARGE CURRENT DISCHARGE CURRENT PULSESLUF PULSES 3O 1X22 ZERO/32 LEVEL DET TO CONTROLLED EQUIPMENT COIN-OPERATED TIMER UTILIZING MEASUREMENT OF ABSOLUTE CAPACITANCE FOR COIN TESTING This invention relates to coin operated mechanisms.

A coin-operated mechanism according to the invention comprises a pair of parallel plates forming an electrical capacitance, the coin being arranged to fall between the plates, and means to measure the change of capacitance caused by the coin and to operate the mechanism if the change falls within a predetermined range.

Preferably the circuit for detecting the change of the capacitance of the plates comprises a signal generator arranged to apply a triangular-wave signal of predetermined amplitude to a first plate of the capacitor, a rectifier connected to a second plate of the capacitance to rectify the resulting square-wave output, and a pair of level detectors connected to the rectifier to detect whether the output falls within a predetermined range. This circuit preferably also incorporates an amplifier to amplify the signal from the second plate before it is rectified.

A delay is preferablyalso incorporated in the circuit to enable the change in capacitance to be monitored again after a set period of time so as to ascertain whether the change in capacitance has persisted for the required period. This is to ensure that the mechanism can only be operated by an object of the correct size.

According to a further feature of the invention, a timing circuit may also be incorporated in the device when it is to be used to control mechanisms which are intended to operate for a fixed period of time for a given amount of money. This timing circuit preferably comprises a timing capacitor whose charge is increased each time a coin is inserted, and which is periodically discharged by a fixed amount by means of a switch.

One application which is envisaged for the timer is for coin operated games, as for example for tennis courts in which the equipment is set up for a fixed period depending on the coin inserted, but many other applications are also possible, for example in parking meters.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a block diagram of the circuit, and

FIG. 2 is a circuit diagram.

Referring to FIG. 1, a signal generator 2 generates a 100 KHZ waveform which is applied to one plate of the coin detector capacitor 4 when a coin is inserted in the apparatus, switching on the power supply by means of a micro-switch (not shown). A current amplifier 6 connected to the other side of the capacitor, amplifies the square wave of current which is induced to flow by the triangular voltage waveform (since the capacitor differentiates the input signal). A rectifier 8 then converts this signal to a d.c. level proportioned to the capacitance 4, at its output.

The output from the rectifier is fed to an upper limit" level detector 10 and a lower limit level detector 12, and if both of these give a satisfactory output when the coin drops through the plates of the capacitance, an AND gate 14 is activated which transmits the signal to a 10 ms delay device 16 which gives an output only if the capacitance remains within the required limits for 10 ms as the coin falls to prevent the appara' tus being operated by larger objects. This output is fed to a monostable 18 which gives a delay of ms when triggered. During the 100 ms delay the circuitry is primed by causing diodes D1 and D2 to conduct and at the same time applying a fixed voltage to D1. This ensures that the timing capacitor voltage starts at the value representing zero time. At the end of the 100 ms delay a switch 20 is operated, which stays on for 30 ms allowing a controlled amount of charge to flow into a luF timing capacitor 22 via the diode D1.

Thus each time a coin is detected the voltage on the timing capacitor is raised by a fixed amount. A low frequency square wave oscillator 24 drives a 30p.s switch 26 which removes a controlled amount of charge from the timing capacitor once every 1.5 seconds. During the intervals when the timing capacitor is not being charged or discharged it is presented with the high reverse impedance of the two very low leakage diodes D1 and D2. A peak voltage sampler 28 gives a continuous output which is equal to the timing capacitor voltage and is connected each time a discharge pulse flows, causing D2 to conduct. A meter 30, connected to the voltage sampler output, gives an indication of time paid for which has not been used up. A zero level detector 32 detects the end of the timed period and givesan output allowing equipment such as tennis post solenoids, to be operated during the timed period.

If the device tampered with and objects other than a coin of the appropriate size are inserted or if coins are lowered and removed on a thread for example, the time left will be reduced to zero and the device will not operate then for a further 60 seconds. This is achieved by the operation of a 60 ms delay 34 indicating that an object has beenpresent in the coin shute for too long, and therefore operating a 60 s switch 36 to discharge the timing capacitor 22 and hold it of for one minute.

In one practical form of the apparatus both 2p and 10p coins are detected in the same shute. A 10p coin gives 20 minutes and a 2p gives 4 minutes. Two additional level detectors are used and the different coins cause different amounts of charge to enter the timing capacitor. Any number of denominations can be detected by the addition of the appropriate circuitry.

FIG. 2 shows a practical circuit corresponding to the block diagram of FIG. 1, which is designed to work with coins of two different values, for example 2 New Pence and 10 New Pence. The overall operation of the circuitry is the same as set out above with reference to the block diagram; and will therefore not be repeated in detail, but the parts of the circuitry corresponding to the blocks of FIG. 1 will be listed in order to enable a better understanding of the invention.

The circuit comprises a signal generator 38 which applies a waveform to the coin shute capacitor 40, which is followed by a current amplifier 42 and a rectifier 44. These feed two sets of level detectors indicated at 46 and 48 respectively. An output 50 from the 2p level detectors 46 feed a monostable 52 and also a monstable 54 via an AND" gate. The monostable 54 is also connected to the output 56 of the 10p level detectors 48 via an AND" gate. The arrangement is such that the monostable 54 will be fired by either coin whilst the monostable 52 will only be fired by a 2p coin. If only the monostable 52 is fired, the circuit will operate for a shorter period.

The lowest level detector also feeds a 60 second switch 58, via a 60 ms delay, (which correspond to the circuit blocks 36 and 34 respectively in FIG. 1) via a line 60.

The outputs A and B of the monostables are connected to respective inputs A and B of a 30 ms switch 62 which switches their output to feed charging pulses into a timing capacitor C13 (corresponding to capacitor 22 of FIG. 1) via line 64 and diode D19 (corresponding to D1 in FIG. 1).

The discharge of the capacitor is controlled by a low frequency square wave generator 66 and a 30 s switch 68 connected to the capacitor C13 via line 70 and diode D18 (corresponding to D1 in FIG. 1). A peak voltage sampler 72 is also connected to discharge diode D18 and is arranged to periodically monitor the voltage on the capacitor C13 and to provide an output via transistor T43 and line 74 to a lmA meter 76 which provides a time left indicator. A zero level" detector 78 determines when the time left has reduced to zero and gives an output to switch off externally arranged solenoids or the like.

The circuitry may be operated by a power supply comprising dry batteries. It takes a very small current, approximately mA during the timed period and zero otherwise. Variation in the battery voltage from 13V to 8V has negligible effect on the accuracy, thus allowing maximum battery life.

Since the coin is detected by the capacitance change it causes when between a pair of parallel metal plates, there are no moving parts except for the coin. Furthermore since the timing circuit operates by extracting small amounts of charge from a capacitor at regular intervals, it is not necessary to have a very low continuous current to control the discharge rate although the capacitor is quite small, (Inf) and the circuitry which detects the voltage level does not need to have a very high input impedance since it only monitors the capacitor voltage for a very small proportion of time.

I claim:

l. A coin operated timing device comprising:

a pair of parallel plates forming an electrical capacitance.

means for guiding a coin to pass between the said plates,

a first timer circuit, said first timer circuiting including a timing capacitor whose charge is increased each time a coin is inserted and which is periodically discharged a fixed amount,

capacitance monitoring means for measuring the absolute value of the capacitance of the parallel plates when the coin is passed between them, said capacitance monitoring means comprising:

a signal generator connected to one of said plates,

a rectifier connected to the other said plate,

a first, upper-level detector connected to the output of the rectifier; and a second, lower-level detector also connected to the said rectifier, and

means for initiating the operation of the timer circuit if the change in the absolute value of the capacitance when the coin passes between the plates falls within a range determined by the level detectors.

2. A coin operated timer as claimed in claim 1 in which the signal generator produces a triangular waveform.

3. A coin operated timer as claimed in claim 1 in which a second timer circuit is provided, which is connected to the output of one of the level detectors and arranged to monitor the time taken for the coin to pass through the plates.

4. A coin operated timer as claimed in claim 1 in which an amplifier is connected between the said other plate and the rectifier.

5. A coin operated timer as claimed in claim 1 in which the first timer circuit is linked to a games-playing apparatus, and means are provided to allow operation of the games-playing device on operation of the timer circuit.

UNITED STATES PATENT OFFICE CEHHCTE @F EQTIN PATENT NO. I 3,929,213 Q DATED 3 December 30, 1975 INVENTOR(S) 1 Richard Verrill It is certified that error appears in the ab0veidentified patent and that said Letters Patent are hereby corrected as shown below;

In the Abstract, change the word "not" to ---to-- in the second last line.

Column 2, line 62, "monstable" should be -monostable-. Q

inc and Scaled this first of June 1976 tscart Arrest:

Rum c. MASON c. MARSHALL DANN Arresting Officer Commissioner nj'Parem: and Trademarks 

1. A coin operated timing device comprising: a pair of parallel plates forming an electrical capacitance, means for guiding a coin to pass between the said plates, a first timer circuit, said first timer circuiting including a timing capacitor whose charge is increased each time a coin is inserted and which is periodically discharged a fixed amount, capacitance monitoring means for measuring the absolute value of the capacitance of the parallel plates when the coin is passed between them, said capacitance monitoring means comprising: a signal generator connected to one of said plates, a rectifier connected to the other said plate, a first, upper-level detector connected to the output of the rectifier; and a second, lower-level detector also connected to the said rectifier, and means for initiating the operation of the timer circuit if the change in the absolute value of the capacitance when the coin passes between the plates falls within a range determined by the level detectors.
 2. A coin operated timer as claimed in claim 1 in which the signal generator produces a triangular waveform.
 3. A coin operated timer as claimed in claim 1 in which a second timer circuit is provided, which is connected to the output of one of the level detectors and arranged to monitor the time taken for the coin to pass through the plates.
 4. A coin operated timer as claimed in claim 1 in which an amplifier is connected between the said other plate and the rectifier.
 5. A coin operated timer as claimed in claim 1 in which the first timer circuit is linked to a games-playing apparatus, and means are provided to allow operation of the games-playing device on operation of the timer circuit. 